1. Field of the Invention
The present invention relates to ultraviolet absorptive laminated resinous articles which exhibit minimized coloring or deterioration induced by ultraviolet radiation, with satisfactory interlayer adhesion and improved abrasion resistance and weatherability.
2. Description of the Prior Art
Resinous films, resinous sheets, resin plates, and other resinous articles (hereinafter may be inclusively referred to as xe2x80x9cresin platexe2x80x9d) made of, for example, polycarbonates are excellent in transparency, impact resistance, heat resistance, flame resistance, and other properties. These resinous articles are in wide use for road constructive materials and building materials and are expected to be applied to other uses. However, the application of the resin plates is restricted since the resin plates are not so effective as metal plates, glass plates and the like in terms of surface hardness, abrasion resistance, solvent resistance and other surface properties. Strong demands have been therefore made to improve the surface properties of such base resin plates. A possible solution to improve the surface properties is a process of -coating the surface of a base resin plate with a surface treatment agent. Such a surface treatment agent include, for example, an ultraviolet-curable acrylic compound, a thermosetting melamine resin, or a thermosetting organopolysiloxane resin which form a hard resin layer on a surface of a base resin plate.
Of these proposed processes, coating the surface of the base resin plate with a thermosetting organopolysiloxane resin that provides typically high surface hardness and chemical resistance. Specifically, by coating the surface of a base resin plate with a partially hydrolyzed condensate of an organotrialkoxysilane alone, with a partially hydrolyzed condensate between a tetraalkoxysilane and an organotrialkoxysilane, or with a partially hydrolyzed condensate of an organotrialkoxysilane containing colloidal silica, the coated resin plate can be obtained with a satisfactory surface hardness. Such a coating constituent of the surface hard resin layer exhibits a satisfactory adhesion to a base resin plate when a base resin plate is made of a poly(methyl methacrylate) resin. However, when coating the surface of polycarbonate resin with these surface treatment agents, the coated hard resin layer tend to decrease its adhesion to the base resin plate and may be peeled from the base resin plate.
To improve the adhesion of such a hard resin layer, Japanese Examined Patent Application Publications No. 63-5155 and No. 63-52668, for example, each propose a technique of preliminarily treating the surface of a polycarbonate resin plate to form a primer layer. Indeed, the adhesion of the surface hard resin layer is improved by forming the surface resin layer on the primer layer, according to this process.
A second problem which generally arises is an insufficient weatherability, particularly deterioration and coloring of the resin plate upon exposure to ultraviolet radiation. An initial adhesion of the hard resin layer is improved by the aforementioned technique, but both the hard resin layer and the primer layer have no property to absorb ultraviolet radiation. Therefore transmitted ultraviolet radiation deteriorates the surface of the resin plate thereby introduces other problems such as deterioration of the improved adhesion of the hard resin layer and deterioration of weatherability such as coloring or decrease in strength. To prevent such ultraviolet radiation that deteriorates the resin from reaching the surface of the resin plate, for example, Japanese Examined Patent Application Publication No. 60-53701 and Japanese Examined Patent Application Publication No. 2-37938 each proposes a technique of adding an ultraviolet absorbent to components of a surface layer such as a primer layer or a surface hard resin layer, and absorbing the ultraviolet radiation by ultraviolet absorbent added layer. In addition, a variety of techniques to improve the composition of the surface hard resin layer or the primer layer have been proposed in order to prevent, for example, deterioration in solvent resistance of the surface layer induced by the added ultraviolet absorbent and to improve the adhesion of the surface layer to a base resin layer (e.g., Japanese Examined Patent Application Publication No. 1-7582, Japanese Examined Patent Application Publication No. 1-32246, Japanese Examined Patent Application Publication No. 1-18944, and Japanese Examined Patent Application Publication No. 2-37938). These techniques can prevent the ultraviolet-induced deterioration of the resin plate surface to some extent and can provide a somewhat satisfactory adhesion.
However, large amounts of an ultraviolet absorbent must be added to the surface hard resin layer and the primer layer in order to provide complete blockage of ultraviolet radiation within these layers. As a result, the surface hard resin layer and/or the primer layer is colored or is hazed to decrease the transparency of the surface hard resin plate, which transparency distinguishes the surface hard resin plate from others. In addition, the added ultraviolet absorbent bleeds out from the layer to deteriorate the appearance of the resin plate or to decrease the abrasion resistance. The bleed-out of the ultraviolet absorbent will result in a deteriorated interlayer adhesion between the surface hard resin layer and the primer layer or between the primer layer and the base resin layer. The ultraviolet absorbent itself does not have a significantly high hardness, and containing large amounts of the ultraviolet absorbent in the hard resin layer will decrease the hardness of the layer. Specifically, without the addition of an ultraviolet absorbent, the surface of the resin plate is deteriorated and the adhesion of the surface hard resin layer is decreased due to ultraviolet radiation. In contrast, the addition of an ultraviolet absorbent results in coloring or deterioration of the surface hardness. These problems have not been solved concurrently.
As a potential solution to these problems, Japanese Unexamined Patent Application Publication No. 9-3135 and Japanese Unexamined Patent Application Publication No. 10-34840, for example, propose the use of an acrylic resin in a surface layer, which acrylic resin is obtained by copolymerizing an acrylic monomer with a reactive ultraviolet absorbent. These techniques allow the use of large amounts of an ultraviolet absorbent. However, all the acrylic resins obtained by the copolymerization with an ultraviolet absorbent are thermoplastic and are insufficient in hardness as a coating layer for surface protection and have an insufficient abrasion resistance. In addition, satisfactory hot water resistance and weatherability cannot be significantly obtained.
Japanese Unexamined Patent Application Publication No. 4-106161 discloses a process for improving the heat resistance, abrasion resistance, surface hardness, surface gloss, and other properties. The process includes the steps of copolymerizing a monomer having an ultraviolet absorptive group to yield a copolymer, coating the surface of a base resin plate with the copolymer as a primer layer, and coating the surface of the primer layer with an organopolysiloxane as a hardcoat layer. The publication also discloses that a monomer having an ultraviolet stable group is preferably copolymerized, in addition to the monomer having an ultraviolet absorptive group.
According to these techniques, however, the constitutive ultraviolet absorptive copolymer is thermoplastic and the primer layer has an insufficient weatherability and a low abrasion resistance even if the surface of the primer layer is coated with a hardcoat layer. As a result, the hardcoat layer has also an insufficient weatherability and a low abrasion resistance. In addition, the adhesion between the primer layer and the hardcoat layer after a hot water resistance test or a weathering test is insufficient and a satisfactory interlayer adhesion cannot be significantly obtained.
Japanese Unexamined Patent Application Publication No. 7-286013 discloses a silyl-group-containing vinyl resin for coating. The vinyl resin is composed of a copolymer comprising a polymerizable silane monomer, another monomer, and a monomer having an ultraviolet stable group as monomer components. The publication states that the vinyl resin provides a coating which is excellent in weatherability, dirt resistance, hardness, and chemical resistance. However, the monomer having an ultraviolet stable group as a monomer component is incorporated in the resin in a relatively low content and the monomer having an ultraviolet stable group has an insufficient ultraviolet absorption property. The vinyl resin is therefore liable to color or to degrade upon exposure to ultraviolet radiation. If a coating of this resin is formed as a thick film to ensure a satisfactory ultraviolet absorption property, cracks are liable to form upon the formation of a surface protective layer on the coating, and the interlayer adhesion between the coating and a hardcoat layer is decreased in such a state as after a hot water resistance test or a weathering test.
U.S. Pat. No. 4,533,595 discloses an abrasion-resistant article of manufacture. This article is obtained by copolymerizing a monomer having an ultraviolet absorptive group to give a copolymer, forming a primer layer of the copolymer on the surface of a base, and forming a hardcoat layer from an organopolysiloxane on the primer layer. However, each constitutive ultraviolet absorptive copolymer of the base protective layer is thermoplastic and the primer layer has an insufficient weatherability and a low abrasion resistance even if the surface of the primer layer is coated with a hardcoat layer. As a result, the hardcoat layer has also an insufficient weatherability and a low abrasion resistance.
In addition, the adhesion between the primer layer and the hardcoat layer after a hot water resistance test or a weathering test is insufficient-and a satisfactory interlayer adhesion cannot be significantly obtained.
The invention has been accomplished to solve these problems that conventional techniques possess, and an object of the invention is to provide a laminated resinous article which has an improved weatherability without introducing ultraviolet-induced coloring, deterioration in surface hardness and interlayer adhesion and has excellent properties such as a high surface hardness and a satisfactory abrasion resistance.
In accordance with the present invention, the invention provides an ultraviolet absorptive laminated resinous article. The resinous article includes a resin base, a base protective layer formed on a surface of the resin base to be protected, and a surface protective layer formed on the base protective layer, and the base protective layer is composed of a cross-linked cured product. The base protective layer includes a polymer obtained by polymerizing a monomer mixture containing 5 to 701 by weight of at least one selected from monomers each having the following formula (1) or (2) and having an ultraviolet absorptive group: 
wherein R1 is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, R2 is a lower alkylene group, R3 is a hydrogen atom or a methyl group, and X is a hydrogen atom, a halogen, a hydrocarbon group having 1 to 8 carbon atoms, a lower alkoxy group, a cyano group, or a nitro group, provided that either R1 or X is a hydrogen atom; 
wherein R4 is a lower alkylene group, and R5 is a hydrogen atom or a methyl group.
The monomer component preferably includes at least one selected from monomers each having the following formula (3) or (4) and having an ultraviolet stable group: 
wherein R6 is a hydrogen atom or a cyano group, R7 and R8 are each independently a hydrogen atom or a methyl group, R9 is a hydrogen atom or a hydrocarbon group, and Y is an oxygen atom or an imino group; 
wherein R6 is a hydrogen atom or a cyano group, R7, R8, R7xe2x80x2, and R8xe2x80x2 are each independently a hydrogen atom or a methyl group, and Y is an oxygen atom or an imino group.
The surface protective layer may be preferably a hardcoat layer to further improve, for example, weatherability, abrasion resistance, and hot water resistance. More preferably, the surface protective layer may include, as a component, at least one resin selected from silicone-based curable resins, and curable resins containing organic polymer-combined inorganic fine particles. The resulting laminated resinous article has a high surface hardness and a satisfactory abrasion resistance with a higher weatherability and a more satisfactory hot water resistance.
When any of the silicone-based curable resins, and curable resins containing organic polymer-combined inorganic fine particles is used as a component of the surface protective layer, additional monomer component to constitute the base protective layer may be preferably used as a copolymer component. The resulting resinous article has a further improved interlayer adhesion between the base protective layer and the surface protective layer. Such additional monomer components include monomers having a reactive silyl group, and more preferably monomers having a hydrolyzable silyl group. Specifically, the copolymer component is preferably at least one selected from monomers shown by the following formula (5) to (7): 
wherein R10 is a hydrogen atom or a methyl group, R11 is a hydrocarbon group having 1 to 6 carbon atoms, xe2x80x9caxe2x80x9d is an integer of from 1 to 3, and b is 0 or 1; 
wherein R12 has the same meaning as defined in R11 or is an alkyloxyalkyl group, and c is 0 or 1; 
wherein R13 has the same meaning as defined in R11, and d is 0 or 1.
The present inventors made intensive investigations to improve the surface hardness, abrasion resistance, weatherability, and other properties, which have been problems in conventional techniques, while maintaining satisfactory transparency, impact resistance, and other properties that a base resin inherently possesses. As a result, they found that the surface hardness, weatherability, and abrasion resistance of a base resin can be improved by forming a layer as a base protective layer on a resin base and forming a surface protective layer on the base protective layer, in which the base protective layer contains an ultraviolet absorptive polymer obtained by polymerizing a monomer component containing a specific amount of a monomer having a specific ultraviolet absorptive group. The present invention has been accomplished based on these findings.
Base resins for use in the invention include, but are not limited to, polycarbonate resins, acrylic resins, polyethylene resins, polyester resins, polypropylene resins, acrylonitrile-butadiene-styrene (ABS) resins, polystyrene resins, and vinyl chloride resins. The resin base may have any shape and may be prepared by any process. A designed resin base with, for example, a woodgrain printing can be also employed.
Components of the base protective layer formed on the resin base, and of the surface protective layer formed on the base protective layer will be described in detail later. The base protective layer is preferably composed of a cross-linked cured product to yield satisfactory weatherability, abrasion resistance, hot water resistance, and other properties as a primary coat for the surface protective layer. As a component of the surface protective layer, at least one resin selected from silicone-based curable resins, and curable resins having organic polymer-combined inorganic fine particles is preferably used. The resulting laminated resinous article has a high surface hardness and a satisfactory abrasion resistance with a further improved weatherability and hot water resistance.
One of main features of the invention is that a base protective layer containing a polymer is formed on a resin base, in which the polymer is obtained by polymerizing a monomer component containing 5 to 70% by weight of at least one selected from monomers of the formula (1) or (2) having an ultraviolet absorptive group. This configuration ensures that ultraviolet radiation is absorbed by the base protective layer before reaching the resin base, and inhibits ultraviolet-induced deterioration or discoloration of the resin base. The monomer does not bleed out as in conventional ultraviolet absorbents added as additives, and can yield a satisfactory interlayer adhesion.
The polymer may further comprise at least one selected from monomers of the formula (3) or (4) having an ultraviolet stable group as a monomer component. The copolymerization with a monomer of this type having an ultraviolet stable group can further improve the weatherability.
When a silicone-based curable resin or a curable resin containing organic polymer-combined inorganic fine particles is used as a component of the surface protective layer, copolymerization with an additional monomer component having a reactive silyl group is preferred to constitute the base protective layer. The additional monomer component is more preferably a monomer component having a hydrolyzable silyl group, typically preferably a reactive monomer component shown by any of the formulae (5) to (7). The adhesion of the resulting base protective layer to the surface protective layer can be further improved. The additional monomer component is used as a component in addition to the above monomer components of the base protective layer.
The monomers of the formula (1) having an ultraviolet absorptive group are benzotriazoles in which R1 is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, R2 is a lower alkylene group, R3is a hydrogen atom or a methyl group, and X is a hydrogen, a halogen, a hydrocarbon group having 1 to 8 carbon atoms, a lower alkoxy group, a cyano group, or a nitro group; and either R1 or X is a hydrogen atom.
In the above formula, the substituent R1includes, but is not limited to, hydrogen atom, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, and other chain hydrocarbon groups; cyclopropyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, and other alicyclic hydrocarbon groups; phenyl group, tolyl group, xylyl group, benzyl group, phenethyl group, and other aromatic hydrocarbon groups. Practical examples of the substituent R2 are alkylene groups each having 1 to 6 carbon atoms, including methylene group, ethylene group, trimethylene group, tetramethylene group, and other straight chain alkylene groups; and propylene group, 2-methyltrimethylene group, 2-methyltetramethylene group, and other branched chain alkylene groups. Illustrative substituents X are hydrogen; fluorine, chlorine, bromine, iodine, and other halogens; methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, and other chain hydrocarbon groups; cyclopropyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, and other alicyclic hydrocarbon groups; phenyl group, tolyl group, xylyl group, benzyl group, phenethyl group, and other aromatic hydrocarbon groups; methoxy group, ethoxy group, propoxy group, butoxy group, pentyloxy group, heptyloxy group, and other lower alkoxy groups having 1 to 6 carbon atoms; cyano group; and nitro group.
Illustrative monomers of the formula (1) having an ultraviolet absorptive group include, but are not limited to,
2-[2xe2x80x2-hydroxy-5xe2x80x2-(methacryloyloxymethyl)phenyl]-2H-benzotriazole,
2-[2xe2x80x2-hydroxy-5xe2x80x2-(methacryloyloxyethyl)phenyl]-2H-benzotriazole,
2-[2xe2x80x2-hydroxy-5xe2x80x2-(methacryloyloxypropyl)phenyl]-2H-benzotriazole,
2-[2xe2x80x2-hydroxy-5xe2x80x2-(methacryloyloxyhexyl)phenyl]-2H-benzotriazole,
2-[2xe2x80x2-hydroxy-3xe2x80x2-tert-butyl-5xe2x80x2-(methacryloyloxyethyl)phenyl]-2H-benzotriazole,
2-[2xe2x80x2-hydroxy-5xe2x80x2-tert-butyl-3xe2x80x2-(methacryloyloxyethyl)phenyl]-2H-benzotriazole,
2-[2xe2x80x2-hydroxy-5xe2x80x2-(methacryloyloxyethyl)phenyl]-5-chloro-2H-benzotriazole,
2-[2xe2x80x2-hydroxy-5xe2x80x2-(methacryloyloxyethyl)phenyl]-5-methoxy-2H-benzotriazole,
2-[2xe2x80x2-hydroxy-5xe2x80x2-(methacryloyloxyethyl)phenyl]-5-cyano-2H-benzotriazole,
2-[2xe2x80x2-hydroxy-5xe2x80x2-(methacryloyloxyethyl)phenyl]-5-tert-butyl-2H-benzotriazole, and
2-[2 xe2x80x2-hydroxy-5xe2x80x2-(methacryloyloxyethyl)phenyl]-5-nitro-2H-benzotriazole. Each of these monomers of the formula (1) having an ultraviolet absorptive group can be used alone or in combination with two or more of these monomers as appropriate.
Monomers of the formula (2) having an ultraviolet absorptive group are benzotriazoles in which the substituent R4 is a lower alkylene group, and the substituent R5 is a hydrogen atom or a methyl group.
Typical examples of the substituent R4in the above formula are alkylene groups each having 2 or 3 carbon atoms, including ethylene group, trimethylene group, and propylene group.
Illustrative monomers of the formula (2) having an ultraviolet absorptive group include, but are not limited to, 2- [2xe2x80x2-hydroxy-5xe2x80x2-(xcex2-methacryloyloxyethoxy)-3xe2x80x2-tert-butylphenyl]-5-tert-butyl-2H-benzotriazole. Each of the monomers of the formula (2) having an ultraviolet absorptive group can be used alone or in combination with two or more of these monomers as appropriate.
The content of the monomer of the formula (1) or (2) having an ultraviolet absorptive group must range from 5 to 70% by weight based on the total weight of monomer components. The lower limit of the range is preferably 10% by weight, more preferably more than 20% by weight, and typically preferably equal to or more than 25% by weight. The upper limit of the range is preferably equal to or less than 60% by weight, and more preferably equal to or less than 50% by weight. A content of the monomer having an ultraviolet absorptive group less than 5% by weight will require a thick base protective layer in order to avoid the ultraviolet-induced degradation of the resin base. This may invite the formation of cracks when the surface protective layer is formed on the base protective layer or during a long-term use. In contrast, a content of the monomer having an ultraviolet absorptive group exceeding 70% by weight may invite deterioration of properties of the base protective layer.
Monomers of the formula (3) or (4) having an ultraviolet stable group are preferably used in the invention and are piperidines in which the substituent R6 is a hydrogen atom or a cyano group, the substituents R7, R8, R7xe2x80x2, and R8xe2x80x2 are each independently hydrogen atom or a methyl group, the substituent R9 is a hydrogen atom or a hydrocarbon group, and the substituent Y is an oxygen atom or an imino group.
Illustrative examples of the substituent R9 include, but are not limited to, hydrogen atom and hydrocarbon groups each having 1 to 18 carbon atoms; including methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, and other chain hydrocarbon groups; cyclopropyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, and other alicyclic hydrocarbon groups; phenyl group, tolyl group, xylyl group, benzyl group, phenethyl group, and other aromatic hydrocarbon groups.
Typical examples of the monomers of the formula (3) having an ultraviolet stable group include,
4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine,
4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine,
4-(meth)acryloyloxy-1,2,2,6,6-pentamethylpiperidine,
4-(meth)acryloylamino-1,2,2,6,6-pentamethylpiperidine,
4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, and
4-crotonoylamino-2,2,6,6-tetramethylpiperidine. Each of these monomers can be used alone or in combination with two or more of these monomers as appropriate. The monomers of the formula (3) having an ultraviolet stable group are not limited to the examples above.
Illustrative monomers of the formula (4) having an ultraviolet stable group are
1-(meth)acryloyl-4-(meth)acryloylamino-2,2,6,6-tetramethyl piperidine,
1-(meth)acryloyl-4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, and
1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine. Each of these monomers may be used alone or in combination with two or more of these as appropriate. The monomers of the formula (4) having an ultraviolet stable group are not limited to the examples above.
The proportion of the monomer of the formula (3) or (4) having an ultraviolet stable group is not critical but is preferably in a range from 0.1 to 15% by weight, more preferable lower limit is 0.5% by weight, typically preferable lower limit is 1% by weight and more preferable upper limit is 5% by weight, typically preferable upper limit is 3% by weight based on the total weight of monomer components of the ultraviolet absorptive polymer constituent of the base protective layer. When the total weight of monomers having an ultraviolet stable group is less than 0.1% by weight, degradation of the base protective layer may not be sufficiently protected. In contrast, when the total weight of the monomers is exceeding 15% by weight, the properties of the base protective layer may be deteriorate.
A monomer having a reactive silyl group is copolymerized as an additional monomer component of the base protective layer in the invention. This additional monomer component most effectively exhibits its advantages when a silicone-based curable resin or a curable resin containing an organic polymer-combined inorganic fine particle is used as a component of the surface cured layer as described above. Of such monomers, typically preferred one is a monomer having a polymerizable double bond and a hydrolyzable silyl group in the molecule. The term xe2x80x9chydrolyzable silyl groupxe2x80x9d as used herein means a group that can form a silanol group by a hydrolysis reaction. Of such monomer components having the hydrolyzable silyl group, monomers of any of the formulae (5) to (7) are typically preferred. Each of these monomers can be used alone or in combination with two or more of these as appropriate.
Monomers of the formula (5) are acrylic monomers each having an alkoxysilyl group, and in the formula (5), R10 is a hydrogen atom or a methyl group, R11 is a hydrocarbon group having 1 to 6 carbon atoms (e.g., methyl group, ethyl group, propyl group, and other alkyl groups; vinyl group, isopropenyl group, allyl group, and other alkenyl groups; and phenyl group, and other aryl groups), xe2x80x9caxe2x80x9d is an integer of 1 to 3, and b is 0 or 1.
Illustrative acrylic monomers having an alkoxysilyl group include, but are not limited to,
3-methacryloxypropyltrimethoxysilane,
3-methacryloxypropyltriethoxysilane,
3-methacryloxypropyltributoxysilane,
3-methacryloxypropyltriisopropoxysilane,
methacryloxymethyltrimethoxysilane,
methacryloxymethyltriethoxysilane,
methacryloxymethyltributoxysilane,
3-acryloxypropyltrimethoxysilane,
3-acryloxypropyltriethoxysilane,
3-acryloxypropyltributoxysilane,
acryloxymethyltrimethoxysilane,
acryloxymethyltriethoxysilane,
acryloxymethyltributoxysilane,
3-methacryloxypropylmethyldimethoxysilane,
3-methacryloxypropylmethyldiethoxysilane,
3-methacryloxypropylmethyldibutoxysilane,
methacryloxymethylmethyldimethoxysilane,
methacryloxymethylmethyldiethoxysilane,
methacryloxymethylmethyldibutoxysilane,
3-acryloxypropylmethyldimethoxysilane,
3-acryloxypropylmethyldiethoxysilane,
3-acryloxypropylmethyldibutoxysilane,
acryloxymethylmethyldimethoxysilane,
acryloxymethylmethyldiethoxysilane, and
acryloxymethylmethyldibutoxysilane. Of these monomers,
3-methacryloxypropyltrimethoxysilane and
3-methacryloxypropylmethyldimethoxysilane are typically preferred, because they can be easily handled and have a high reactivity and be crosslinked in a high density.
Monomers of the formula (6) are vinyl functional compounds having an alkoxysilyl group, and monomers of the formula (7) are vinyl functional alkoxysilane compounds. These compounds of the formula (6) or (7) are vinyl-functional monomers, in which each of R12 and R13 has the same meaning as defined in R11 or is an alkyloxyalkyl group, and each of c and d is 0 or 1.
Illustrative examples of these vinyl functional monomers include, but are not limited to, vinyltrimethoxysilane,
vinyltriethoxysilane, vinyltributoxysilane,
vinyltriacetoxysilane, vinyptris(2-methoxyethoxy)silane,
vinpylmethyldimethoxysilaned vinylmethyldiethoxysilane
vinylmethyldibutoxysilane,
vinylmethylbisa(2-meathoxyethoxy)silane,
3-vinyloxypropyltrimethoxysilane,
3-vinyloxypropyltriethoxysilane,
3-vinyloxypropylmethyldimethoxysilane, and
3-vinyloxypropylmethyldiethoxysilane. Of these monomers,
vinyltrimethoxysilane, vinyltriethoxysilane, and
3-vinyloxypropyltrimethoxysilane are typically preferred, because they can be easily handled and have a high reactivity.
When the monomer having a hydrolyzable silyl group is employed as a copolymer component,.silanol groups formed by a hydrolysis reaction are condensed to each other to form a cross-linkable moiety in the resulting copolymer. This copolymer having a cross-linkable moiety and constituting the base. protective layer can be cured by heat to thereby improve the surf ace hardness and weatherability of the base protective layer. In addition, the presence of the silanol groups enhances adhesion of the base protective layer to the resin base and to the surface protective layer formed on the base protective layer. This advantage is typical to a surface protective layer made of a silicone-based curable resin or a curable resin containing an organic polymer-combined inorganic fine particle. As a result, the interlayer adhesion as a laminated resinous article can be markedly improved.
The proportion of the monomer component having a reactive silyl group is not critical, but is preferably 2 to 70% by weight, more preferable lower limit is 5% by weight and more preferable upper limit is 50% by weight to the weight of the copolymer that occupies a major proportion of the base protective layer, in order to effectively exhibit the operations of the monomer component having a reactive silyl group.
A copolymerization ratio of the monomer component having a reactive silyl group less than 2% by weight results in an insufficient adhesion of the base protective layer to the surface protective layer after a weathering test or a hot water resistance test. In contrast, the copolymerization ratio exceeding 70% by weight invites an excessively hard copolymer and :results in an insufficient adhesion to the surface protective layer after a weathering test, or a decreased storage stability of the copolymer.
The polymer having an ultraviolet absorptive group as a main component of the base protective layer for use in the invention can further comprise additional copolymerizable monomers, as far as the additional monomers do not deteriorate various required properties of the polymer. From the viewpoint of the weatherability, a monomer of the following formula (8) is preferably employed: 
wherein R14 is a hydrogen atom or a methyl group, and Z is a hydrocarbon group having 4 or more carbon atoms.
In the above formula, the substituent Z includes, cyclohexyl group, methylcyclohexyl group, cyclododecyl group, and other alicyclic hydrocarbon groups each having 4 or more carbon atoms; butyl group, isobutyl group, tert-butyl group, 2-ethylhexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, pentadecyl group, octadecyl group, and other straight-chain or branched-chain alkyl groups each having 4 or more carbon atoms; bornyl group, isobornyl group, and other polycyclic hydrocarbon groups each having 4 or more carbon atoms. Among these groups, alicyclic hydrocarbon groups, branched-chain alkyl groups, and straight-chain alkyl groups having 6 or more carbon atoms are preferred.
Illustrative monomers of the formula (8) include, but are not limited to, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate, stearyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Each of these monomers can be used alone or in combination with two or more of these.
The proportion of the monomer of the formula (8) is not critical but is preferably in a range from 3 to 70% by weight, and more preferably in a range from 5 to 50% by weight based on the total monomer components of the ultraviolet absorptive polymer. If the proportion is less than 3% by weight, the activity for improving the weatherability obtained by the copolymerization of this monomer cannot be significantly exhibited. In contrast, if the proportion exceeds 70% by weight, the interlayer adhesion of the base protective layer to the resin base might be deteriorated. The use of a monomer having an epoxy group or of vinyl acetate as a monomer component can more effectively enhance the interlayer adhesion of the base protective layer containing the resulting copolymer to the base resin and to the surface protective layer, and can yield a further higher weatherability. Preferred monomers having an epoxy group include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, (meth)acrylates containing an alicyclic epoxy group (xe2x80x9cCYCLOMER M-100xe2x80x9d and xe2x80x9cCYCLOMER A-200xe2x80x9d, products of Daicel Chemical Industries, Ltd., Japan). The content of these monomers in the copolymer is preferably in a range from 1 to 10% by weight.
Other copolymerizable monomers include (meth)acrylic acid, itaconic acid, maleic acid, maleic anhydride, and other monomers containing a carboxyl group; 2-(meth)acryloyloxyethyl acid phosphate, and other acid phosphate-based monomers; 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone-modified hydroxy(meth)acrylates (e.g., trade name xe2x80x9cPLACCEL FMxe2x80x9d, a product of Daicel Chemical Industries, Ltd.), and other monomers containing a group having an active hydrogen; methyl (meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, isopropyl(meth)acrylate, and other lower alkyl esters of (meth)acrylic acid; (meth)acrylamide, N,Nxe2x80x2-dimethylaminoethyl(meth)acrylate, imide(meth)acrylate, N-methylol(meth)acrylamide, and other nitrogen-containing monomers; ethylene glycol di(meth)acrylate, and other monomers each having two polymerizable double bonds; vinyl chloride, vinylidene chloride, and other halogen-containing monomers; styrene, xcex1-methylstyrene, vinyltoluene, and other aromatic monomers; and vinyl ether. The copolymerizable monomers are not limited to the examples above. Each of these monomers can be used alone or in combination with two or more of these as necessary.
Of these additional monomers, typically preferred to improve the properties of the base protective layer are monomers each having a polymerizable double bond and a cross-linkable functional group. Such monomers include, for example, monomers having a polymerizable double bond and a cross-linkable functional group. Such monomers include hydroxylalkyl (meth)acrylates and epoxy-group-containing (meth)acrylates. Copolymers obtained by the copolymerization of any of these monomers can be cured by a cross-linking reaction when the copolymer is used in combination with a polyisocyanate compound or another curing agent or a cationic polymerization catalyst, as described below. Thus, the surface hardness, weatherability, adhesion to the surface protective layer, of the base protective layer, and the abrasion resistance of the surface protective layer can be further improved. Among them, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and other hydroxyalkyl (meth)acrylates are typically preferred from the viewpoint of low cost.
The content of the monomers having a polymerizable double bond and a cross-linkable functional group in the copolymer constituent of the base protective layer is preferably 1 to 50% by weight and more preferable lower limit is 3% by weight and more preferable upper limits 30% by weight. A content of the monomers less than 1% by weight results in an insufficient adhesion of the base protective layer to the surface protective layer after a weathering test or a hot water resistance test. In contrast, a content of the monomers exceeding 50% by weight provides an excessively hard copolymer and thus a decreased adhesion to the surface protective layer after a weathering test.
A technique for blending the monomers in the preparation of the copolymer constituent of the base protective layer is not critical, and any known or conventional blending technique can be employed.
In addition, a polymerization process for copolymerizing a monomer composition is not critical and includes solution polymerization, dispersion polymerization, suspension polymerization, emulsion polymerization, and other known polymerization processes. A solvent is used in the polymerization of the monomer composition according to the solution polymerization process. Such solvents include, but are not limited to, toluene, xylene, and other aromatic solvents; isopropyl alcohol, n-butyl alcohol, and other alcohol solvents; propylene glycol methyl ether, dipropylene glycol methyl ether, ethyl Cellosolve, butyl Cellosolve, and other ether solvents; butyl acetate, ethyl acetate, Cellosolve acetate, and other ester solvents; acetone, methyl ethyl ketone, methyl isobutyl ketone, diacetone alcohol, and other ketone solvents; and dimethyl formamide. Solvents for use in the polymerization are not limited to these solvents, but solvents which are erosive to the base rein should be avoided. Each of the solvents can be used alone or in combination as a mixture. The amount of the solvent may be selected from an appropriate range in consideration of, for example, the concentrations of products.
A polymerization initiator is used in the copolymerization of the monomer composition. Such polymerization initiators include, 2,2xe2x80x2-azobis-(2-methylbutyronitrile), tert-butyl peroxy-2-ethylhexanoate, 2,2xe2x80x2-azobisisobutyronitrile, benzdyl peroxide, di-tert-butyl peroxide, and other conventional radical polymerization initiators. The amount of the polymerization initiator is not critical and can be appropriately determined according to required characteristics of the polymer. The amount of the polymerization initiator is preferably in a range from 0.01 to 50% by weight, and more preferably in a range from 0.05 to 20. %.by weight relative to the total weight of the monomer components.
Where necessary, at least one chain transfer agent is effectively added to the monomer composition to control the molecular weight of the resulting copolymer. Such chain transfer agents include, for example, n-dodecyl mercaptan, t-dodecyl mercaptan, n-butyl mercaptan, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethxysilane, 3-mercaptopropylmethyldiethoxysilane, (CH3O)3Sixe2x80x94Sxe2x80x94Sxe2x80x94Si(OCH3)3, and (CH3O)3Sixe2x80x94S4xe2x80x94Si(OCH3)3. The continuous addition of a chain transfer agent having a hydrolyzable silyl group in the molecule, such as 3-mercaptopropyltrimethoxysilane, into a solution containing the monomer mixture is preferred. The use of a chain transfer agent of this type can control the molecular weight and can introduce hydrolyzable silyl groups into terminals of vinyl monomers.
The reaction temperature is not critical but is preferably in a range from room temperature to 200xc2x0 C., and more preferably in a range from 40xc2x0 C. to 140xc2x0 C. The reaction time may be appropriately set to a sufficient time to complete the polymerization reaction, according to the composition of the monomer composition and the type of the polymerization initiator.
The weight average molecular weight (Mw) of the ultraviolet absorptive polymer is not critical but is preferably in a range from 2,000 to 500,000, more preferably from 4,000 to 300,000, and typically preferably from 5,000 to 250,000. The weight average molecular weight is measured by gel permeation chromatography (GPC) with a polystyrene standard.
The formation of the base protective layer will now be described in detail. The above-prepared ultraviolet absorptive polymer is mixed, where necessary, with another polymer to yield a base protective layer-producing composition, and the composition is applied onto the resin base to yield a base protective layer. The base protective layer may be formed directly onto the resin base or may be formed onto a primer layer which is formed on the surface of the resin base. The composition can be applied onto the resin base by dipping, spray coating, blush coating, curtain flow coating, gravure coating, roller coating, spin coating, bar coating, electrostatic coating, or another technique. The applied base protective layer-producing composition is then cured by heating or by irradiation of ultraviolet rays or electron beam to yield a base protective layer.
The ultraviolet absorptive polymer alone can be cured when the copolymer contains, for example, an epoxy group or a (meth)acryloyl group in addition to the reactive silyl group. The copolymer of this type can be cured through cation polymerization or radical polymerization induced by heat or irradiation with ultraviolet rays or electron beam. Where necessary, a cation polymerization catalyst or a radical polymerization catalyst is used in the polymerization.
If the ultraviolet absorptive polymer cannot be cured by itself, a curing agent should be preferably added to the polymer. Such a curing agent is a compound or a polymer each containing two or more functional groups per molecule, which functional groups are reacted through cross-linking curing reaction with a curable functional group in the ultraviolet absorptive polymer. Such curable functional groups include, for example, a hydroxyl group, an amino group, a carboxyl group or its anhydride, an epoxy group, and an amido group. The curing agent may be selected and employed according to the type of the functional group in the ultraviolet absorptive polymer. For example, illustrative curing agents include polyisocyanate compounds or modified products thereof, aminoplast resins, epoxy resins, oxazoline-group-containing resins, and other cross-linking curing agents, when the functional group in the ultraviolet absorptive polymer is a carboxyl group or its anhydride; cross-linking curing agents made of compounds containing, for example, amines, carboxylic acids, amides, or N-methylolalkyl ethers, when the functional group is an epoxy group; polyisocyanate compounds or modified products thereof, epoxy resins, aminoplast resins and other cross-linking curing agents, when the functional group is a hydroxyl group or an amino group. Of these curing agents, isocyanate compounds, epoxy resins, and aminoplast resins are preferred in combination with the group having an active hydrogen.
When a monomer component having a reactive silyl group is used as the copolymer constituent of the base protective layer, the reactive silyl group introduced into the copolymer molecule allows the copolymer to be curable. However, a curing catalyst is effectively used to further enhance the curing. Such curing catalysts for use in the reaction include, but are not limited to, dibutyltin dilaurate, dibutyltin dimaleate, dioctyltin dilaurate, tin octanoate, and other organic tin compounds; phosphoric acid, monomethyl phosphate, monoethyl phosphate, monobutyl phosphate, monooctyl phosphate, monodecyl phosphate, dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dioctyl phosphate, didecyl phosphate, and other phosphoric acid or phosphoric esters; alkyl titanates; tris(ethyl acetoacetate)aluminium, and other organic aluminium compounds; tetrabutyl zirconate, tetrakis(acetylacetonato)zirconium, tetraisobutyl zirconate, butoxytris(acetylacetonato)zirconium, and other organic zirconium compounds; maleic acid, adipic acid, azelaic acid, sebacic acid, itaconic acid, citric acid, succinic acid, phthalic acid, trimellitic acid, pyromellitic acid, and anhydrides of these acids, p-toluenesulfonic acid, and other acidic compounds; hexylamine, di-2-ethylhexylamine, N,N-dimethyldodecylamine, dodecylamine, and other amines; mixtures or reaction products between these amines and acidic phosphoric esters; sodium hydroxide, potassium hydroxide, and other alkaline compounds.
Typically preferred examples of these curing catalysts are organic tin compounds, acidic phosphoric esters, mixtures or reaction products between an acidic phosphoric ester and an amine, saturated or unsaturated polycarboxylic acids or anhydrides thereof, reactive silicon compounds, organic titanate compounds, organic aluminium compounds, and mixtures of these compounds, because these compounds have a particularly high catalytic activity.
The proportion of the curing catalyst to the copolymer is preferably in a range from 0.01 to 10% by weight and more preferably in a range from 0.05 to 5% by weight relative to a monomer component unit having a reactive silyl group in the copolymer.
Where necessary, the base protective layer-producing composition containing the copolymer having an introduced reactive silyl group may effectively further comprise a dehydrating agent to suppress hydrolysis of the silyl group during storage and subsequent deterioration of storage stability. Such dehydrating agents include, but are not limited to, methyl orthoformate, ethyl orthoformate, methyl orthoacetate, ethyl orthoacetate, methyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, methyl silicate, ethyl silicate, and other hydrolyzable ester compounds. Each of these compounds can be-used alone or in combination with two or more of these. These hydrolyzable ester compounds can be added to a copolymerization system in any stage prior to, during, or after the copolymerization, when the composition contains a vinyl-based monomer component having a reactive silyl group as a copolymerizable component.
The polymers (i.e., ultraviolet absorptive polymers) to be a main component of the base protective layer in the invention are as described above. According to the invention, each of these ultraviolet absorptive polymers can be used alone or in combination with any of additional polymers. The ratio of the additional polymers to main component in the base protective layer is preferably 40% or less, more preferably 30% or less, and most preferably 20% or less by weight. Such additional polymers are other thermoplastic polymers, or thermosetting polymers that can be cross-linked and cured alone or by the aid of a cross-linking agent. The type and the amount of the additional polymers can be appropriately selected according to the application and required characteristics of the invented resinous article. Such additional polymers include, but are not limited to, vinyl chloride resins, polyester resins, acrylic resins, silicon resins, and other thermoplastic polymers; urethane resins, aminoplast resins, silicon resins, epoxy resins, and other thermosetting polymers that can be cured alone; polyester resins, acrylic resins, epoxy resins, and other thermosetting resins that are cured by the aid of a curing agent.
Each of the cross-linking agents for use herein can be employed alone or in combination with two or more of these. The amount of the curing agent may be determined according to, for example, the type of the curing agent, and the molar ratio of a curable functional group in the base protective layer to a functional group in the curing agent is preferably in a range from 0.8 to 1.2. A cross-linking catalyst may be added to a reaction system to enhance a cross-linking reaction. Such cross-linking catalysts include, for example, salts, inorganic substances, organic substances, acid substances, and alkali substances.
When the base protective layer is cured by heating, the temperature depends on the type of the cross-linking functional group or the type of the curing agent for use in the reaction, and the curing temperature is preferably in a range of, for example, from room temperature to 250xc2x0 C.
When the base protective layer is cured by ultraviolet irradiation, a curing process may be determined according to, for example, the species of a used photopolymerization initiator and a light source for generating ultraviolet rays, and the distance between the light source and a surface to be applied. For example, the base protective layer is cured by irradiating ultraviolet radiation having a wavelength of 1,000 to 8,000 angstroms for, generally, several seconds, and at longest for several ten seconds.
Alternatively, the base protective layer may be cured by electron beam irradiation, for example, by irradiating an electron beam at an accelerating voltage of, usually, 50 to 1,000 keV and preferably 100 to 300 keV at an absorbed dose of about 1 to 20 Mrad. The electron beam may be irradiated in the air but should be preferably irradiated in an inert gas such as nitrogen gas. If necessary, the base protective layer may be further heated after ultraviolet irradiation or electron beam irradiation to further enhance the curing.
The thickness of the base protective layer depends on the amount of copolymerized monomers having an ultraviolet absorptive group, according to the Lambert-Beer""s law and is not critical as far as satisfying a desired weatherability of the resin base or required properties of the surface protective layer. The thickness should preferably fall in a range from 0.5 to 200 xcexcm, more preferably from 1 to 100 xcexcm, and typically preferably from 2 to 30 xcexcm. A thickness of the base protective layer exceeding 200 xcexcm will decrease an application speed and may deteriorate inherent properties of the resin base. In contrast, a thickness of the base protective layer less than 0.5 xcexcm will inhibit a uniform application of the composition onto the resin base and may deteriorate the ultraviolet absorption performance.
Another feature of the invention is a surface protective layer formed on the base protective layer. According to the invention, the ultraviolet absorptive polymer constituent of the base protective layer is a curable resin, and preferably a curable resin having reactive silyl group, and this configuration improves the hardness, hot water resistance, weatherability, and other properties. In addition, the surface protective layer having a high surface hardness formed on the base protective layer can dramatically improve the surface hardness, abrasion resistance and weatherability with satisfactory hardness, hot water resistance, and weatherability of the primary layer.
A component resin of the surface protective layer is not critical but is preferably at least one resin selected from silicone-based curable resins, and curable resins having organic polymer-combined inorganic fine particles. These resins can provide satisfactory surface hardness, weatherability, abrasion resistance, interlayer adhesion, and other properties.
Such silicone-based curable resins are resins each having a siloxane bond and include, for example, partial hydrolysates of a trialkoxysilane and a tetraalkoxysilane or alkylated products of these compounds; hydrolyzed products of a mixture of a methyltrialkoxysilane and a phenyltrialkoxysilane; and products of partial hydrolysis and condensation of an organotrialkoxysilane containing colloidal silica. Such silicone-based curable resins are commercially available as, for example, xe2x80x9cSi COAT 2xe2x80x9d (a product of Daihachi Chemical Industry Co., Ltd., Japan); xe2x80x9cTOSGARD 510xe2x80x9d, xe2x80x9cUVHC 8553xe2x80x9d, xe2x80x9cUVHC 8556xe2x80x9d, and xe2x80x9cUVHC 8558xe2x80x9d (products of Toshiba Silicone Corporation, Japan); xe2x80x9cKP-851xe2x80x9d, xe2x80x9cKP-854xe2x80x9d, xe2x80x9cX-12-2206xe2x80x9d, xe2x80x9cX-12-2400xe2x80x9d, and xe2x80x9cX-12-2450xe2x80x9d (products of Shin-Etsu Silicones, Japan); xe2x80x9cSOLGARD NP 720xe2x80x9d, xe2x80x9cSOLGARD NP 730xe2x80x9d, and xe2x80x9cSOLGARD RF 0831xe2x80x9d (products of Nippon Dacro Shamrock Co., Ltd.). These resins contain an alcohol or other products formed in a condensation reaction. Where necessary, the resins can be further dissolved or dispersed in an appropriate organic solvent, water, or a mixture of these substances. Such organic solvents for use in the dissolution or dispersion include, but are not limited to, lower fatty acid alcohols, polyhydric alcohols and ethers and esters thereof. The surface protective layer may further comprise a variety of surfactants to yield a smooth surface. Such surfactants include, for example, siloxane-based surfactants, alkyl fluoride-based surfactants, and other surfactants.
The term xe2x80x9corganic polymer-combined inorganic fine particlexe2x80x9d means a composite inorganic fine particle having an organic polymer fixed on the surface of the inorganic fine particle. When the surface protective layer is formed from a curable resin containing the fine particle, the surface hardness and other properties of the resultant product can be improved. Practical examples and details of production processes of the organic polymer-combined inorganic fine particle are described in Japanese Unexamined Patent Application Publication No. 7-178335, Japanese Unexamined Patent Application Publication No. 9-302257, and Japanese Unexamined Patent Application Publication No. 11-124467.
Curable resins to be incorporated with organic polymer-composite inorganic fine particles are not critical and include, for example, melamine resins, urethane resins, alkyd resins, acrylic resins, and multifunctional acrylic resins. Such multifunctional acrylic resins include polyol acrylates, polyester acrylates, urethane acrylates, epoxy acrylates, and other resins.
Such curable resins containing the organic polymer-combined inorganic fine particles are commercially available as, for example, xe2x80x9cUWC-3300xe2x80x9d and xe2x80x9cUWC-3600xe2x80x9d (products of Nippon Shokubai Co., Ltd., Japan).
The surface protective layer is formed by applying a film of a layer-producing composition onto the surface of the base protective layer and heating the applied film (heat curing process), or irradiating an active energy ray such as ultraviolet rays, electron beams or radioactive rays to the applied film (active energy ray curing process). Of these processes, silicone-based curable resins are mainly cured by the heat curing process, and curable resins containing organic polymer-combined inorganic fine particles are generally cured by the heat curing process or the active energy ray curing process using ultraviolet rays or electron beams. Generally, the heat curing process is inferior to the active energy ray curing process in that the former requires a longer time for the base protective layer to be cured. However, if the base protective layer is excessively cured, the interlayer adhesion between the base protective layer and the surface protective layer may be decreased after a hot water resistance test or a weathering test. Accordingly, the curing time should be preferably selected appropriately.
The layer-producing composition for the formation of the surface protective layer is applied to the resinous article by, for example, dipping, spray coating, flow coating, roller coating, or spin coating. To improve the interlayer adhesion, the surface protective layer may be formed on an intermediate layer such as an undercoat, a primer layer, or an adhesive layer. Silane coupling agent (e.g., xe2x80x9cA-187xe2x80x9d, xe2x80x9cA-189xe2x80x9d, xe2x80x9cA-1100xe2x80x9d, and xe2x80x9cA-1120xe2x80x9d, trade names, products of Nippon Unicar Co., Ltd., Japan) and other additives can be added to the composition.
The thickness of the surface protective layer is in a range from 0.1 to 200 xcexcm, preferably in a range from 0.5 to 100 xcexcm, and typically preferably in a range from 1 to 50 xcexcm. A thickness of the surface protective layer less than 0.1 xcexcm results in an excessively low surface hardness to exhibit advantages as a surface protective layer. In contrast, a thickness of the surface protective layer exceeding 200 xcexcm deteriorates the properties, particularly bending strength and other mechanical strengths, of the resin plate.
The base protective layer and the surface protective layer may further comprise a variety of additives in addition to the above additives. Such additives include, but are not limited to, leveling agents; titanium white, and other pigments; pigment dispersants; antioxidants; viscosity modifiers; light stabilizers; metal deactivators; peroxide decomposing agents; fillers; plasticizers; lubricants; rust inhibitors; fluorescent whiteners; flow control agents; and antistatic agents, for use in paints and other layer-producing compositions.
The invention has the feature in that a specific base protective layer made of a cross-linked and cured product is formed on a surface of the resin base to be protected, and a surface protective layer is formed on the base protective layer, as described above. In addition, the properties as a laminate resinous article can be further effectively improved by imparting a heat shielding property to the resin base. For example, resin bases obtained in the following manners are also effectively used. A heat shielding substance is kneaded into a composition prior to molding of a resin base and the resulting composition is molded to yield a film or sheet resin base having a heat shielding property. Alternatively, a coating composition containing a, heat shielding substance is applied onto one or both surfaces of a molded resin base to yield a resin base having a,heat shielding property.
Such heat shielding substances for use in the invention are not critical as far as substances have absorption in a near-infrared region (700 to 1800 nm). However, in some uses, substances exhibiting less coloring in a visible light region (400 to 700 nm) and having a large molar absorption coefficient are preferred. Each of these substances can be employed alone or in combination with two or more of these. Separately, in some applications, toning in a visible light region may be performed or a substance having absorption in a visible light region may be incorporated to color the resinous article to a target color.
Such heat shielding substances include organic heat shielding substances and inorganic heat shielding substances.
The total amount of the organic heat shielding substances to be used depends on the application, difference in molar absorption coefficients of the substances to be used or combination of the substances and cannot be uniquely determined. The total amount of the organic heat shielding substances is generally in a range from 0.01 to 50 g/m2, and typically preferably in a range from 0.1 to 20 g/m2 relative to the base resin.
Preferred organic heat shielding substances include metal complex compounds, phthalocyanines, naphthalocyanines, aminium salts, anthraquinones, and naphthoquinones. Of these substances, typically preferred are phthalocyanines having a nitrogen atom bonded to at least one, preferably at least four, of phthalocyanine skeletons (e.g., phthalocyanines substituted with a phenylamino group or an alkylamino group). Phthalocyanines described in, for example, Japanese Unexamined Patent Application Publication No. 5-345861, Japanese Unexamined Patent Application Publication No. 6-264050, and Japanese Unexamined Patent Application Publication No. 6-25548 can be advantageously employed.
The inorganic heat shielding substances include, but are not limited to, metals, metallic nitrides, metallic nitride-oxides, metallic carbides, and metallic oxides. Typically preferred inorganic heat shielding substances are fine particles of metallic oxides, because these substances have a satisfactory solubility for a dispersion medium and a good weatherability. Such preferred metallic oxides include, for example, indium oxide or indium oxide-based oxides comprising indium oxide and a tetravalent metallic element and/or F; tin oxide or tin oxide-based oxides comprising tin oxide and a pentavalent metallic element and/or F; zinc oxide-based oxides comprising zinc oxide and at least one element selected from Group IIIB metallic elements, Group IVB metallic elements, and other trivalent metallic elements, tetravalent metallic elements, F, and C; cadmium stannate, and other metallic oxides.
Of the indium oxide-based oxides comprising indium oxide and a tetravalent metallic oxide and/or F, typically preferred are indium oxide-based oxides comprising indium oxide and tin, a tetravalent metallic element. The ratio of the metallic element to tin in the metallic oxides is preferably in a range from 0.1 to 20% by weight. Practical examples of the zinc oxide-based oxides comprising zinc oxide and at least one element selected from Group IIIB metallic elements, Group IVB metallic elements, and other trivalent metallic elements, tetravalent metallic elements, F, and C are zinc oxides containing at least one selected from Al, Ga, In, and Tl as Group IIIB metallic elements, Si, Ge, Sn, and Pb as Group IVB metallic elements, and Ti, V, Cr, Mn, Fe, Co, Zr, Hf, La, and other trivalent and tetravalent metallic elements. The ratio of each metallic element to zinc in the metallic oxides is preferably in a range from 0.1 to 20% by weight.
These metallic oxide fine particles should preferably have a mean particle diameter of 0.1 xcexcm or less, more preferably 0.05 xcexcm or less, and particularly preferably 0.03 xcexcm or less, as such fine particles can provide an excellent transparency.
Of the metallic oxides, zinc oxide-based oxides are available at low cost and are desirable. Especially, zinc oxide-based oxides containing at least one element selected from Group IIIB metallic elements and Group IVB metallic elements have a high transparency in the visible light region and have a satisfactory heat shielding property, and can be advantageously employed. The zinc oxide-based oxides are desirable in that they can have an ultraviolet shielding property by changing the species and amount of the metallic element to be incorporated.